A three-dimensional isolator with adaptive stiffness property

ABSTRACT

The present invention discloses a three-dimensional seismic and vibration isolator with adaptive stiffness property in both vertical and horizontal directions. The isolator comprises an upper connection plate, a middle plate, an under connection plate, a disc spring, pre-compressed helical springs, a laminated lead rubber bearing, and viscous dampers. The upper connection plate, middle connection plate and under connection plate are made of high strength low carbon steel with high loading capacity. The upper connection plate and middle plate are tightly contacted by the occlusive design, to guide the vertical motion. The vertical isolation system is made up of the disc spring, pre-compressed helical spring, and viscous damper. The horizontal isolation system comprises the laminated rubber bearing, pre-compressed helical spring and viscous damper. The invention adopts the theory of nonlinear adaptive vibration control technology and can be used to protect building structures or instruments from the seismic strikes or other environmental vibrations.

CROSS REFERENCE TO RELATED PATENT APPLICATION

The present application is the US national stage of PCT/CN2018/074901filed on Feb. 1, 2018, which claims the priority of the Chinese patentapplication No. 201710969015.2 filed on Oct. 18, 2017, which isincorporated herein by reference.

BACKGROUND OF THE PRESENT INVENTION 1. Field of Invention

The present invention is a new three-dimensional isolation system forbuildings or large-scale facilities to reduce the seismic hazards orenvironment vibration harassment. It belongs to the field of vibrationcontrol of structures.

2. Description of Related Arts

Base isolation technology is considered one of the most significantinventions in the field of earthquake engineering in the 20^(th)century. Many isolated buildings have been built worldwide. The basicprinciple of the isolation technology is to set a soft isolation layerat the bottom of a building, generally by adopting seismic isolators tobear the upper gravity load and to reduce the horizontal stiffness. Theisolation system works as a filtering system to mitigate the seismicinduced acceleration response and dissipate input energy. Modernisolation technology has 60 years of history, and it belongs to a typeof passive control strategy.

Nevertheless, the traditional seismic isolators have two main drawbacks:(1) Vertical earthquake or environment vibration cannot be reduced. Manyfield observation after earthquakes and numerical analysis have revealedthat the vertical component of an earthquake would cause damage onstructural components or non-structural component of a building. Withthe development of the city transit lines, the metro vibration,especially its vertical component would affect the living comfort of theresidents. (2) The trade-off between isolation effect and isolationdisplacement. For most normal earthquakes, a better isolation effect canbe obtained by designing a soft isolation layer to have a more extendednatural period. However, this results in a larger displacement inisolation layer which would cause disastrous consequence if thedisplacement exceeds the safe range.

SUMMARY OF THE PRESENT INVENTION

In order to overcome the drawbacks mentioned above, the presentinvention discloses a novel three-dimensional (3D) isolator withadaptive stiffness, which can isolate vertical earthquake and microenvironmental vibration and can have an optimized horizontal seismicisolation effect.

The present invention discloses a three-dimensional isolator withadaptive stiffness, comprising an upper connection plate (1), a middleplate (2), an under connection plate (3), a disc spring (4), helicalspring (5), a laminated rubber bearing (6), pre-compressed helicalsprings (7), and viscous dampers (8), Wherein the laminated rubberbearing is designed between the middle and the under connection plates.One side of helical spring is placed at the first groove on the middleplate, and the disc spring is placed on the middle plate outside thehelical spring. The other side of the helical spring inserts into thesleeve of the second groove on the upper connection plate to keep theworking stability of the helical spring. The viscous dampers aredesigned symmetrically beside the middle plate with the two endsconnecting the upper and under connection plate using the sphericalhinges. Pre-stressed helical spring is set outside the viscous damper,and it can accommodate the relative displacement between upper and underconnection plate in any directions. An inner lead core is designed atthe center of the laminated rubber bearing to dissipate motion energy inhorizontal and vertical directions. In the vertical direction of the 3Disolator, the disk spring and helical spring work in parallel. When theisolator is applied with the upper gravitational load, the disk springcan provide negative stiffness and helical spring provides positivestiffness. Thus, the vertical isolation system can have a quasi-zerostiffness property. In the horizontal direction of the 3D isolator, thelead laminated rubber bearing and pre-stressed helical spring work inparallel. The pre-stressed helical spring can provide negative stiffnesswhen the horizontal displacement is small but positives stiffness whenthe horizontal displacement is large. The horizontal isolation system ischaracterized by adaptive stiffness by adding the pre-stressed helicalspring.

In the present invention, the viscous dampers and lead core are added todissipate the motion energy in both vertical and horizontal directions.

In the present invention, the upper connection plate and middleconnection plate contact tightly with each other, to lock the relativehorizontal and rotational motion.

The upper connection platel and the middle plates 2 are tightlycontacted by the occlusive design, to guide the vertical motion byconstraining the relative displacement.

In the present invention, the disk spring, helical spring and outsidepre-stressed helical spring can bear the upper gravity load together inparallel in both static and dynamic state.

In the present invention, the two connection ends of the pre-stressedhelical spring are welded with the spherical hinge so that the helicalspring can provide tensile force for the isolation system.

In the present invention, the upper connection plate and middleconnection plate are contacted tightly by the occlusive design, todecouple the vertical and horizontal motion in the isolator. Theocclusive design between the upper and middle connection plate can lockthe relative horizontal and rotational motion to allow only relativevertical displacement between the two connection plates. Thus, thepresent invention decouples the horizontal and vertical displacement,which means the vertical displacement only occurs between the upper andmiddle connection plates and the horizontal displacement only occursbetween middle and under connection plates. Due to the occlusive design,the vertical and the horizontal isolation system can work independently,and the rocking behavior can be avoided by locking the relativerotational motion.

In the present invention, in the vertical direction of the isolator, thehelical spring and disk spring work in parallel. When the gravity loadof super-structure applies on the top of the isolator at a gravitybalance state, the disk spring deforms near the flat position. At theflat position, the disk spring can provide negative stiffness. Combinedwith the positives stiffness provided by the helical spring, thevertical isolation system can have the quasi-zero stiffness property,thus can effectively isolate the vertical earthquake component andenvironmental vibrations.

In the present invention, in the horizontal direction of the isolator,the pre-stressed helical spring and laminated rubber bearing work inparallel. Due to the pre-stressed load in the helical spring, it canprovide negatives stiffness when the horizontal displacement is small toobtain better isolation effect and provide positive stiffness when thedisplacement is significant to help prevent overly large displacement.

In the present invention, the viscous dampers are placed vertically toconnect the upper and under connection plate, thus to dissipate thehorizontal and vertical motion energy.

In the present invention, a viscous damper is placed inside thepre-stressed helical spring to keep the working stability of the spring.

The principle of the present invention is illustrated as follows.

The present invention introduces adaptive stiffness design to improvethe isolation performance of the traditional laminated lead rubberbearing (existing technology). The adaptive stiffness technology belongsto a kind of nonlinear passive vibration control strategy, which meansthe stiffness of the system can vary with the displacement. For thepresent invention, the adaptive stiffness property means the system canprovide little stiffness when the displacement is small, but largestiffness when the displacement is large.

In the vertical direction of the isolator, the quasi-zero stiffnessisolation system (also characterized by adaptive stiffness property) isobtained by the parallel combination of the disk spring and helicalspring. Quasi-zero stiffness (QZS) system means that the stiffness ofthe system is approximate to zero at the gravity balance state. Thequasi-zero stiffness system is a kind of strong nonlinear isolationsystem which can adequately solve the contradiction between satisfactoryisolation effect and high gravity loading capacity which exists intraditional linear isolation system. Besides, the QZS system is kind ofpassive system that can obtain high-static but low-dynamic stiffnesswithout external energy input. The vertical isolation system can have agood isolation performance for seismic and environment vibrations.Meanwhile, it can well control the overly large vertical displacement.

And in the horizontal direction of the isolator, the adaptive stiffnessisolation system consists of the parallel combination of the laminatedlead rubber bearing and pre-stressed helical springs. The laminatedrubber bearing can support the top load and provide main restoringcapability for the system. The additional pre-stressed device can givethe adaptive property to the system by providing negative stiffness atsmall displacement state, and positive stiffness at large displacementstate.

For the present invention, the size and mechanic parameters of thecomponents, including the disk spring, helical spring, pre-stressedhelical spring, laminated rubber bearing, etc., can be designedaccordingly based on the engineering requirement. The invention has goodfeasibility and a promising application prospect.

Compared with the existing seismic isolators or vibration reductiontechnologies (such as traditional laminated rubber isolator, frictionpendulum bearing), the advantages of the present invention are:

-   -   (1) The present invention can isolate earthquakes or environment        vibrations in three directions. Both the horizontal and vertical        isolation systems are characterized by the adaptive stiffness        property which has a superior isolation effect than traditional        techniques.    -   (2) The present invention can better ensure the isolation safety        under most unfavorable considered earthquakes or drastic impact.        The adaptive property allows the isolation system to have larger        restoring stiffness to help constrain the excessive isolation        displacement.    -   (3) Viscous dampers and the lead core can work together to        dissipate earthquake energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of the present invention in initialstate;

FIG. 2 is a three-dimensional assembly drawing of the present invention;

FIG. 3 is an installation schematic view of the invention, and aschematic view of the isolation layer;

FIG. 4 is a schematic structure view of the viscous damper;

FIG. 5 is a schematic structure view of the laminated lead rubberbearing;

FIG. 6 is a three-dimensional view of the upper connection plate;

FIG. 7 is a three-dimensional view of the middle connection plate.

The illustration of the numbers in the figures:

-   -   1 upper connection plate,    -   101 inner radius of the second groove,    -   102 inner sleeve    -   2 middle connection plate,    -   201 outer radius of the middle connection plate,    -   202 inner radius of the middle connection plate,    -   3 under connection plate,    -   4 disc spring,    -   5 helical spring,    -   6 laminated lead rubber bearing,    -   7 pre-stressed helical spring,    -   8 viscous damper,    -   9 spherical hinge,    -   10 upper embedded part,    -   11 under embedded part,    -   12 the upper isolation layer column,    -   13 the under isolation layer column,    -   14 guide rod,    -   15 valve,    -   16 damping hole,    -   17 viscous liquid,    -   18 upper seal plate of the laminated lead rubber bearing,    -   19 lead core,    -   20 under seal plate of the laminated lead rubber bearing,    -   21 rubber layer,    -   22 steel layer,    -   23 outer layer of rubber covering.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

The present invention is further explained in detail according to theaccompanying drawings. The present invention reveals a three-dimensionalseismic and vibration isolator with adaptive stiffness propertyaccording to FIG. 1 to FIG. 7.

Referring to FIG. 1 of the drawings, the invention of thethree-dimensional isolator with adaptive stiffness property, includes anupper connection plate 1, a middle connection plate 2, an underconnection plate 3, a disc spring 4, helical spring 5, a laminated leadrubber bearing 6, pre-stressed helical spring 7, viscous damper 8 andspherical hinge 9. The disk spring 4, the helical spring 5 and thelaminated lead rubber bearing 6 work in parallel as the verticalquasi-zero stiffness (QZS) isolation system. The laminated lead rubberbearing 6 and the two springs are vertically connected in series tosupport the upper gravity load. The viscous damper 8 is set inside thepre-stressed helical spring 7. The top and bottom ends of the viscousdamper 8 and pre-stressed helical spring 7 all are connected withspherical hinge 9, thus both to connect the upper connection plate 1 andunder connection plate 3, also to accommodate relative motion in anydirections.

The upper connection plate 1 and the middle connection plate 2 arecontacted tight by occlusive design to allow only relative verticalmotion.

The vertical gravity load of the isolated structure is transmitted tothe upper connection plate 1 and then supported by the disc spring 4,the helical spring 5, and pre-stressed spring 7 together. Each of theviscous dampers 8 does not provide damping force in the static state.The helical spring 5 and the two connection plates (1 and 2), thepre-stressed helical spring 7 and the spherical hinge 9, all areconnected using soldering so that the helical spring 5 and pre-stressedhelical spring 7 can provide force in the tensile direction. Thetelescopic viscous damper is set inside the pre-stressed helical springand also connects both ends in welded connection to keep the workstability and can provide damping force in the tensile direction. Thespherical hinge 9 is designed to connect the combination of thepre-stressed helical spring 7 and the viscous damper 8 with the upperconnection plate 1 and the under connection plate 3, to accommodaterelative motion between the two plates in any directions. The laminatedlead rubber bearing 6 is connected tightly with the middle connectionplate 2 and connection plate 3 using high-strength bolts.

Referring to FIG. 2 of the drawings, the assembly diagram of the presentinvention is shown in the 3D view.

Referring to FIG. 3 of the drawings, the present invention is installedin the isolation layer at the base of a building structure. The upperembedded part 10 and the under embedded part 11 are embedded into thebottom of the upper isolation layer column 12 and under isolation layercolumn 13 respectively before casting the concrete. Based on the loadingcapacity design, the disc spring 4 is deformed at around its flatposition. The helical spring 5 and pre-stressed helical spring 7 alsosupport the vertical gravitational load.

Referring to FIG. 4 of the drawings, the assembly of the viscous damper8 of the present invention is shown. The guide rod 14 connects tightlywith the valve 15, to put the valve in motion within the viscous liquid17 to dissipate the motion energy when the viscous liquid 17 flowthrough the damping holes 16 on the valve 15.

Referring to FIG. 5 of the drawings, it shows the assembly of thelaminated lead bearing 6 of the present invention. The upper seal plate18 and under seal plate 20 can connect the bearing with othercomponents. The outer rubber cover layer 23 can protect the bearing(lead core 19, rubber layers 21 and steel layers 22) from theenvironment, to enhance the durability of the bearing.

Embodiment 2 Further Innovation of Embodiments

In this further invention, the upper connection plate 1 and middleconnection plate 2 contact tightly with each other, to lock the relativehorizontal and rotational motion. Thus, only relative verticaldisplacement is allowed, which also means that the present inventiondecouples the vertical and horizontal motion.

Referring to FIG. 6 and FIG. 7, the outer radius 201 of the middleconnection plate 2 and the inner radius 101 of the second groove of theupper connection plate 1 is equal. The middle connection plate 2 cantightly embed into the second groove of upper connection plate 1. Theengagement of the two plates can lock the relative horizontal androtational motion.

Specifically for example, when the present invention ofthree-dimensional isolator with adaptive stiffness property supports thegravity load of the upper building, relative vertical displacementoccurs between the upper connection plate 1 and the middle connectionplate 2 and the two plates contact tightly. The engagement due to thegravity load can lock the relative horizontal and rotational motion,thus to realize the motion decoupling between the horizontal andvertical directions.

What is claimed is:
 1. A three-dimensional isolator with adaptivestiffness property, comprising an upper connection plate (1), a middleplate (2), an under connection plate (3), a disc spring (4), helicalspring (5), a laminated rubber bearing (6), pre-compressed helicalsprings (7), and viscous dampers (8), wherein The laminated rubberbearing (6) connects the middle plate (2) and the under connection plate(3); The first groove is designed at the top of the middle plate (2) andthe second groove is at the bottom of the upper connection plate (1); Ahelical spring (5) is inserted into the two grooves to remain workstability and get through the disc spring (4) from the inner hole; Thedisc spring (4) and helical spring (5) work in parallel to transferforce between the middle plate (2) and the upper connection plate (1);The viscous dampers (8) are designed symmetrically by the side of themiddle plate (2); both ends of a damper (8) are connected to the upperand under connection plates accordingly, using spherical hinges (9); thespherical hinge (9) can accommodate relative displacement between theupper and under connection plates in any directions; the pre-compressedhelical springs (7) is set at the outside of the damper (8) and weldedto the spherical hinge (9) so that it can carry load both in compressionand tension state; An inner lead core (19) is designed at the center ofthe laminated rubber bearing (6) to dissipate motion energy inhorizontal and vertical directions; In the vertical direction of theisolator, the disc spring (4) and helical spring (5) are set inparallel; when the gravity is applied at the top, the disc spring (4)can provide negative stiffness and the helical spring (5) can providepositive stiffness to obtain a quasi-zero stiffness isolation system; Inthe horizontal direction, the laminated lead rubber bearing (6) andpre-stressed helical spring (7) work in parallel; the pre-stressedhelical spring (7) is designed as an adaptive stiffness device; when thehorizontal displacement of the isolator is small, the spring can providenegative stiffness to optimize the isolation effect, but when thedisplacement is large, it will provide positive stiffness to helpconstrain excessive displacement.
 2. The three-dimensional isolator withadaptive stiffness property as in claim 1, wherein the viscous dampers(8) and lead core (19) are added to dissipate the motion energy in bothvertical and horizontal directions.
 3. The three-dimensional isolatorwith adaptive stiffness property as in claim 1, wherein the upperconnection plate (1) and middle connection plate (2) contact tightlywith each other, to lock the relative horizontal and rotational motion.4. The three-dimensional isolator with adaptive stiffness property as inclaim 1, wherein the two connection ends of the pre-stressed helicalspring (7) are welded with the spherical hinge (9) so that the helicalspring (7) can provide tensile force for the isolation system.
 5. Thethree-dimensional isolator with adaptive stiffness property as in claim1, wherein the outer radius (201) of the middle connection plate (2) andthe inner radius (101) of the second groove of the upper connectionplate (1) is equal; the middle connection plate (2) can tightly embedinto the second groove of upper connection plate (1); the engagement ofthe two plates can lock the relative horizontal and rotational motion;The occlusive design is realized by designing the external diameter ofthe middle connection plate (2) equals to the inner diameter of thesecond groove on the upper connection plate (1); The static relativevertical displacement between the upper and middle connection platesoccurs with gravity load applied, and the two parts interlock each otherin the horizontal direction.